Generally, filament-reinforced plastics include continuous fibers for reinforcement such as glass fibers or carbon fibers embedded in plastics, which typically have relatively low mechanical strength. Such filament-reinforced plastics exhibit superior properties in terms of mechanical strength, rigidity and impact strength to short fiber-reinforced thermoplastics having a length of 1 mm or less or to long fiber-reinforced plastics such as long fiber-reinforced thermoplastics (LFT) or glass mat-reinforced thermoplastics (GMT), which have a length of 5 to 50 mm.
Further, filament-reinforced plastics need to have flexibility so as to be woven in a single or two directions such that the woven filament-reinforced plastic structure may be applied to products requiring various mechanical properties.
The filament-reinforced plastics are typically produced through pultrusion or a process of commingling followed by hot pressing.
In pultrusion, widely dispersed bundles of filaments are passed through dies or a bath containing a liquid (or melt) resin so as to impregnate the plastic resin into the bundles of filaments. Although pultrusion can increase the degree of impregnation under optimal process conditions, it is difficult to regulate the amounts of the reinforcing fibers (that is, filaments) and the plastic resin, and to weave the filament-reinforced plastics due to low flexibility.
In the process of commingling followed by hot pressing, filaments and a fiber plastic resin are commingled and then subjected to hot pressing. Since the filaments do not lose inherent flexibility of fibers even after physical coupling between the filaments and the plastic resin through commingling and hot pressing, the commingled filaments can be easily woven, exhibit excellent formability and impregnability upon hot pressing after weaving, and allow easy adjustment of the amounts of the reinforcing filament and the plastic resin in the filament-reinforced plastics.
In the process of commingling followed by hot pressing, however, since the plastic resin is randomly mingled with the bundle of filaments, the plastic resin is partially insufficiently impregnated into the bundle of filaments upon hot pressing after weaving, thereby deteriorating uniformity of physical properties. In addition, when the plastic resin is prepared in the form of fibers, there is a drawback in that only thermoplastic materials having sufficient elongation in relation with processibility can be restrictively used.
Therefore, there is an urgent need for an apparatus for producing a thermoplastic/filament hybrid composite, which can be easily woven, exhibit excellent impregnation uniformity and impregnability upon melt impregnation after weaving, and allows application of various kinds of thermoplastics.